Preparation of polyhalo-copper phthalocyanines having a high color strength

Abstract

Finely divided, agglomerated crude polyhalo-copper phthalocyanine is recrystallized (conditioned) by heating the crude pigment with benzoic acid, toluic acid, ethylbenzoic acid or a mixture of these, in the presence of water, at from 80° to 130° C. The resulting polyhalo-copper phthalocyanine pigments are readily dispersible and of high color strength, and pigmentary forms ranging from transparent to high-hiding can be obtained in a selective manner. The carboxylic acids used as conditioning media can readily be recovered by acidifying the mother liquor.

I claim: 
     
       1. In a process for preparing a polyhalocopper phthalocyanine having high color strength by recrystalliation of a finely divided, agglomerated crude polyhalcopper phthalocyanine in an organic aqueous phase at elevated temperatures, the improvement comprising heating said crude polyhalocopper phthalocyanine to 80°-130° C. with benzoic acid, toluic acid, ethylbenzoic acid, or a mixture thereof, and maintaining said elevated temperature until the desired pigmentary form has formed. 
     
     
       2. A process as claimed in claim 1, wherein the weight ratio of crude pigment to the carboxylic acids is from 1:0.5 to 1:2. 
     
     
       3. A process as claimed in claim 1, wherein benzoic acid, o-toluic acid, m-toluic acid, 2-, 3- or 4-ethylbenzoic acid or a mixture of these carboxylic acids is used. 
     
     
       4. A process as claimed in claim 1, wherein the mixture is heated at from 90° C. to boiling point.